Lott links to the Boston Globe discussing the increase in crime since Massachusetts passed a gun control package in 1998. The number of guns registered in Massachusetts dropped 86% following that law's passage, so clearly it had a major effect on legal gun owners. The effect on murders with guns was also significant: it nearly doubled from 65 in 1998 to 122 in 2011. Aggravated assaults and robberies with firearms rose 20-30%.
Some blame the failure of the gun control laws on surrounding states with laxer laws, but it's generally illegal (for handguns, at least) to purchase firearms outside your state of residence without going through a licensed dealer, so that can't possibly be the problem.